1. Field of the Invention
The present invention relates to a method for manufacturing a liquid discharge head substrate, to be employed for a liquid discharge head.
2. Description of the Related Art
Well known liquid discharge heads are the descriptively named inkjet heads that today are so often employed in printers to discharge ink. Generally, for such an inkjet head, a substrate is provided that includes: discharge ports, through which ink is to be discharged; energy generation elements, used to generate the energy required for the discharge of ink through the discharge ports; an ink supply port, to which and through which ink is to be supplied; and ink flow passageways, which communicate with the ink supply port and the discharge ports and along which ink is supplied to the discharge ports. The discharge ports, the energy generation elements and the ink flow passageways are arranged on the obverse face of the substrate, while the ink supply port is an opening, an ink passageway, leading from the reverse to the obverse side of the substrate. Thus, ink can be supplied from the reverse of the substrate to the ink flow passageways and, impelled by a driving force engendered by energy generation elements located along these paths, discharged through the discharge ports.
A requirement for a head substrate having the above arrangement, to facilitate the downsizing of the substrate and to stabilize the discharge function, is that on the reverse of the substrate the supply port opening width (hereinafter referred to as a reverse opening width) be narrowed. And when multiple ink supply ports are to be formed in a substrate, narrowing their reverse opening widths becomes especially important.
To form an ink supply port that passes through a substrate, orientation-dependent anisotropic wet etching is employed; however, with this method, anisotropy consonant with crystal orientation occurs between the direction of the depth of etching and the direction of the width. FIG. 11 is a schematic, cross-sectional view of a head substrate manufactured using a conventional method. Referring to FIG. 11, the reverse opening width of a supply port 34 formed in a substrate 30 is determined by the width of the substrate 30 obverse side opening (hereinafter referred to as an obverse opening width). For example, when the substrate 30 is made of silicon, and when the obverse opening width is W2, the thickness of the substrate 30 is D and the reverse opening width is W1, the reverse opening width W1 is determined by the relation equation W1=W2+2D/tan 54.7°.
Therefore, in order to reduce the reverse opening width W1, either the obverse opening width W2 must be narrowed, or the thickness D of the substrate 30 must be reduced.
Therefore, proposed in U.S. Pat. No. 6,805,432 is a head substrate manufacturing method according to which, to reduce the reverse opening width, neither a narrowing of the obverse opening width nor a reduction in the thickness of the substrate is required.
The manufacturing method described in U.S. Pat. No. 6,805,432 is one whereby a non-perforating hole is formed using a mask, formed on the reverse of a substrate and by performing anisotropic dry etching, and thereafter, an ink supply port is formed using the same mask and by performing orientation-dependent anisotropic wet etching.
According to U.S. Pat. No. 6,805,432, the manufacturing method disclosed therein will form an ink supply port having a smaller reverse opening width than a case wherein an ink supply port having the same obverse opening width is formed by performing only orientation-dependent anisotropic wet etching.
However, in order for the obverse opening width to be increased without the reverse opening width being changed, the amount of material removed by anisotropic dry etching must be increased. In other words, the depth to which anisotropic dry etching is performed must be greater. However, when the amount of material to be removed by anisotropic dry etching is increased, the etching period is extended and inkjet head substrate productivity is reduced. On the other hand, when the substrate is thinned to reduce the etching period, the strength of the substrate would be reduced.